Changes in Fecal Calprotectin After Rifaximin Treatment in Patients With Nonconstipated Irritable Bowel Syndrome.

Background: Fecal calprotectin, an indicator of colonic inflammation, is associated with nonconstipated irritable bowel syndrome. Rifaximin is an antibiotic used to treat nonconstipated irritable bowel syndrome. We performed a retrospective review of patient charts to investigate the changes in fecal calprotectin levels and intestinal symptoms following treatment with rifaximin in patients with nonconstipated irritable bowel syndrome with elevated fecal calprotectin.

Methods: This study included 198 patients presenting with gastrointestinal complaints consistent with Rome III criteria for irritable bowel syndrome. We treated them with rifaximin for 4-12 weeks, until fecal calprotectin levels were normalized, and divided these into 4-, 8-, and 12-week groups according to the treatment period. Fecal calprotectin levels and gastrointestinal symptoms were assessed following rifaximin therapy.

Results: A total of 162 subjects achieved normalized fecal calprotectin values. Of these, most patients who used rifaximin for 8 or 12 weeks showed a significant improvement in gastrointestinal symptoms by the fourth week of treatment, and gradually improved symptoms after 4 weeks. Fecal calprotectin levels were reduced with concomitant improvement of clinical symptoms. In addition, 36 patients who had elevated fecal calprotectin even after 12 weeks of rifaximin treatment showed a gradual reduction in gastrointestinal symptoms and fecal calprotectin during the course of treatment for 12 weeks.

Conclusions: These findings suggest that fecal calprotectin might be a useful biomarker for measuring the effect of rifaximin therapy in nonconstipated irritable bowel syndrome patients with elevated fecal calprotectin values.